[pve-devel] Volume live migration concurrency

[Fabian Grünbichler]

> Andrei Perapiolkin via pve-devel <pve-devel at lists.proxmox.com> hat am 26.05.2025 16:31 CEST geschrieben:

> Hi Proxmox Community,
> 
> I'm curious whether there are any standard or guidelines that govern the 
> order in which the methods: /activate_volume, deactivate_volume, path/ 
> are called during VM live migration.
> 
> Assuming the storage plugin supports `live migration`:
> 
> 1. Can/path/ be called before /activate_volume?/

yes

> 2. When /vm /migrates from/node1/ to/node2, /might /activate_volume/ 
> on/node2/ be invoked before /deactivate_volume/ has completed on /node1?
> /

it has to be, for a live migration both the source VM and the target VM need
access to the volume. the migration ensures that only either copy/node is
writing to a shared volume at any given time. for a local volume, the volumes
are independent anyway.

> 3. In the context of live migration: Will Proxmox skip calling 
> /deactivate_volume/ for snapshots that have already been activated? 
> Should the storage plugin explicitly deactivate all snapshots of a 
> volume during migration?

a live migration is not concerned with snapshots of shared volumes, and local
volumes are removed on the source node after the migration has finished..

but maybe you could expand this part?